The present invention relates to an ultrasound diagnostic apparatus and a method for producing an ultrasound image, and particularly to an ultrasound diagnostic apparatus and a method for producing an ultrasound image of a vascular wall.
Conventionally, ultrasound diagnostic apparatuses using ultrasound images have been employed in the medical field. In general, this type of ultrasound diagnostic apparatus comprises an ultrasound probe having a built-in transducer array and an apparatus body connected to the ultrasound probe. The ultrasound probe transmits ultrasonic waves toward a subject, receives ultrasonic echoes from the subject, and the apparatus body electrically processes the reception signals to produce an ultrasound image.
In addition, such an ultrasound diagnostic apparatus may acquire various kinds of information indicative of the condition of a disease based on reception signals obtained by receiving ultrasonic echoes from the subject. For example, ultrasonic waves are transmitted to and received from a blood vessel, and the resulting reception signals are used to acquire information such as elastic characteristics of a vascular wall, a thickness of the vascular wall and a thickness of the vascular diameter in circulatory diseases including arteriosclerosis and cerebral infarction. Values included in such information vary with the progression of arteriosclerosis, so that the condition of a circulatory disease can be estimated by observing the values.
However, since the thickness of a vascular wall is small and also is affected by pulsation due to cardiac beats, the information on the blood vessels as described above contains a significant amount of noise components. Accordingly, there is a demand for an ultrasound diagnostic apparatus capable of measuring the state of a blood vessel while suppressing the noise components.
As a technology for accurately measuring the state of a blood vessel, an ultrasound diagnostic apparatus that tracks a position of a vascular wall based on a reception signal to identify positions of a front wall and a rear wall of a blood vessel, based on which a change-waveform of a blood vessel is generated, thereby measuring changes in the vascular diameter over time has been proposed, as disclosed by JP 2004-290408 A.
The ultrasound diagnostic apparatus presented by JP 2004-290408 A can accurately measure the state of a blood vessel by identifying pulsating timing using electrocardiographic waveforms and, based on the pulsating timing, removing noise components associated with cardiac beats from a change-waveform of a blood vessel. However, there was a problem that, due to the necessity of obtaining electrocardiographic waveforms in addition to ultrasound information, the apparatus would increase in size to thus impair its mobility, resulting in poor applicability for diagnosis in various places.